#ifndef __LIB_DIV64_H__
#define __LIB_DIV64_H__

/*
 * do_div() is NOT a C function. It wants to return
 * two values (the quotient and the remainder), but
 * since that doesn't work very well in C, what it
 * does is:
 *
 * - modifies the 64-bit dividend _in_place_
 * - returns the 32-bit remainder
 *
 * This ends up being the most efficient "calling
 * convention" on x86.
 */
#define do_div(n,base) ({ \
    unsigned long __upper, __low, __high, __mod, __base; \
    __base = (base); \
    asm("":"=a" (__low), "=d" (__high):"A" (n)); \
    __upper = __high; \
    if (__high) { \
      __upper = __high % (__base); \
      __high = __high / (__base); \
    } \
    asm("divl %2":"=a" (__low), "=d" (__mod):"rm" (__base), "0" (__low), "1" (__upper)); \
    asm("":"=A" (n):"a" (__low),"d" (__high)); \
    __mod; \
  })

#endif  // __LIB_DIV64_H__
